The continuing demand for increasing computational power and memory space is driving the miniaturization of integrated circuits and their component parts. For instance, the aggressive scale-down of metal oxide semiconductor (MOS) transistor critical dimensions has shrunk the length and width dimensions of the source/drain electrode into the nanometer regime. One concern arising from this scale down is that an increased sheet resistance of smaller dimensioned salicided source/drain electrodes will decrease the drive current of the MOS transistor for a given gate-drain capacitance.
Previous efforts to maintain the drive current within acceptable limits, as the critical dimensions of the MOS transistors are scaled down, have focused on changing the metals used in the source/drain electrode. Specifically, with each reduction in technology node, lower resistivity metals have been used. Thus, metal salicide source/drain electrode have transitioned from titanium salicide to cobalt salicide, and now currently to nickel salicide. The transition to different metal salicides is not without problems however. Colbalt salicides are subject to resistivity degradation due to the well-known necking phenomenon observed at device feature sizes of less than about 90 nanometers. Nickel salicides, while having a lower resistivity than titanium or cobalt salicides, suffers from thermal instability and the formation of spike defects that can extend into the channel region of the transistor, resulting in shorts and increased leakage current.
Accordingly, what is needed in the art is a method of increasing drive current in semiconductor devices that is compatible with existing metal salicide source/drain electrode fabrication schemes that overcomes the above-mentioned problems, and in particular that minimizes source/drain electrode resistivities at technology nodes of about 90 nanometers and lower.